The present invention is related to the field of eye controllable screen pointer systems that use eye gaze tracking devices.
An eye controllable screen pointer system comprises either an eye gaze tracking means or a head tracking means, or both, working in combination with a screen. In such an application, choices are usually displayed in different areas of the screen, and the user selects a choice by looking at it, i.e. by directing his gaze at it. The system infers where on the screen the user is directing his gaze at from eye gaze tracking information and/or head tracking information that is made available by their respective means. Often, and for feedback to the user, the system also projects a mark at the point of the screen that the system inferred that the user is looking at.
Since the head tracking problem was solved before the eye gaze tracking problem, the earlier systems were head tracking only systems. The user would wear a helmet, and was assumed to be gazing straight ahead. The user would move his head (thus also moving the helmet) to face exactly one of the choices displayed on the screen. A classic such system is described in U.S. Pat. No. 4,349,815 to Spooner. Head movement is registered by the perceived helmet movement. Another example of a head tracking only system is U.S. Pat. No. 4,682,195 to Davison. An ultrasonic signal tracks the position and orientation of a helmet with respect to the screen. Similarly, light pen systems (such as the one taught in U.S. Pat. No. 4,565,999 to King et al.) require head movement. In such head tracking only systems, only head movement is registered. Even if the user shifts his eye gaze to a direction other than straight ahead, such is not registered.
Most of the prior art solves the head tracking problem from a reference point of the screen. The approach assumes that the screen is stationary, and tracks the head movement. The approach has drawbacks, such as requiring expensive components to implement. Additionally, the prolonged head movement required to operate a head tracking only system is tiring to the user""s neck.
Eye gaze tracking means are those means that detect which direction the user is gazing at, with respect to his face. The direction of the eye gaze is detected by methods such as the corneal reflection method, described in U.S. Pat. No. 5,231,674 to Cleveland. Eye gaze tracking only systems generally require the user to not move his head, because that could introduce lateral error. That requirement can make a user""s neck stiff, because a healthy user will ordinarily move his head slightly. Alternately, some lateral error can be tolerated, but that would be at the expense of the screen resolution not being very high (which would allow ultimately fewer choices to be displayed on the screen).
Most systems of the prior art utilize either head tracking means only, or eye gaze tracking means only. But even systems that combine both head tracking and eye gaze tracking are characterized by the high expense resulting from including the head tracking components.
It is an object of the present invention to provide an eye controllable screen pointer that has none of the disadvantages of the prior art.
It is another object of the present invention to provide an eye controllable screen pointer that permits ordinary head movement of the user, while having none of the disadvantages of the head tracking techniques.
It is yet another object of the present invention to provide a simplified eye controllable screen pointer that uses a single input device for both a head tracking function and an eye gaze tracking function.
It is one more object of the present invention to provide an eye controllable screen pointer that can be manufactured economically.
According to the present invention, an eye controllable screen pointer system is provided that uses eye gaze tracking while simultaneously bypassing the problems of head tracking. The eye controllable pointer system of the present invention reverses the frame of reference of the head tracking problem, by treating the actual ordinary head movement of the user as instead an apparent movement of the screen with respect to the user""s head. Thus, instead of performing head tracking, the screen pointer system of the present invention performs screen tracking with respect to the user""s head. Screen tracking is performed by a screen tracking camera, attached to a helmet the user is wearing. The screen tracking camera is aided by either light emitted from a screen beacon located near the screen, or by a light pattern emitted by the screen itself as a screen beacon signal. The screen tracking camera provides a screen tracking signal. Eye gaze tracking is performed as is known in the art, or according to a novel way described herein. An eye gaze tracking means is also attached to the helmet, and provides an eye tracking signal. The information carried in the screen tracking signal and in the eye tracking signal are combined in a calculation by a processing means residing in a processor to produce a point of computed gaze on the screen. In an alternate embodiment of the invention, the input device of both the eye gaze tracking means and the screen tracking camera are combined into a single video camera, thus resulting in a simplified apparatus. Optionally, the system further projects a mark at the point of computed gaze.
A main advantage of the present invention with respect to the prior art is a significantly lower cost, resulting from the lower cost of the screen tracking components compared to those required for head tracking. This and other objects and advantages of the present invention will be more appreciated and understood after a consideration of the following drawings and the detailed description of the invention.